This invention is directed to a high voltage power supply, and, in particular, a high voltage power supply having a multiplier circuit located therein, with the multiplier circuit mounted on a movable plate, such that the positive output and negative output of the multiplier circuit can be selectively switched to provide either a positive or negative high voltage output.
There are many known power supplies in the prior art and three such power supplies are diagrammatically represented in FIGS. 1A, 1B and 1C. In particular, the prior art power supply shown in FIG. 1A includes conventional control circuits 100 coupled to a conventional driver circuit 102. The driver circuit is connected via a transformer 104 to a conventional Cockcroft-Walton multiplier 106. The output of the Cockcroft-Walton multiplier provides the generic high voltage output which is filtered and modified to provide a clean high voltage output. This is a manual high voltage power supply, which means that the user must reconfigure the high voltage circuits by physically disconnecting and connecting key electrical nodes. In particular, the dashed lines 108 indicate the manual links required in order to obtain a positive polarity high voltage output. When dashed lines 108 are connected, solid lines 110 must be disconnected. Alternatively, if a negative polarity high voltage output is desirable, the links shown by the dashed lines 108 must be removed and the electronic links indicated by the solid lines 110 must be connected manually. The circuitry of FIG. 1A requires the high voltage electrodes to be accessed by the user, and presents a safety hazard by exposing the user to energized high voltage circuits. This technique also requires significant time to perform the switchover from positive polarity to negative polarity, thereby making it impracticable for automated system requirements.
With reference to FIG. 1B, a more advanced manual system is provided, including control circuits 112 coupled to driver circuit 114, which is connected via a transformer 116 to a center feed Cockcroft-Walton multiplier circuit 118. By providing a center feed Cockcroft-Walton multiplier circuit, rather than the convention Cockcroft-Walton shown in FIG. 1A, the number of manual links is reduced. In particular, the user would be required to connect dashed wires 120 for a positive polarity high voltage output, and alternatively, solid lines 122 are required to obtain a negative polarity high voltage output. Thus, it can be seen that the total number of manual links that must be connected and disconnected to change the polarity is reduced from six to four. However, this reduction in number of connections does not change the fact that a user is exposed to energized high voltage circuitry which presents a safety hazard. Furthermore, the reduction in number of manual links from six to four does not significantly increase the switchover time in order to make this construction practical for an automated system.
Particular reference is now made to the prior art of FIG. 1C, which illustrates an advancement over the manual technique of FIGS. 1A and 1B. In particular, the circuitry of FIG. 1C includes control circuits 130 electrically connected to driver circuit 132 which is connected via a low voltage relay 134 to either high voltage transformer 136 or high voltage transformer 138. High voltage transformer 136 is connected to Cockcroft-Walton multiplier 140 and high voltage transformer 138 is connected to Cockcroft-Walton multiplier 142. A high voltage relay 144 is connected to the output of Cockcroft-Walton multipliers 140 and 142 and is synchronized with low voltage relay 134. Thus, if a positive polarity is desired the low voltage relay 134 and high voltage relay 144 selectively switch to couple Cockcroft-Walton multiplier 140 to driver 132 and high voltage output 146. Alternatively, if a negative polarity high voltage output is desired the low voltage relay 134 and high voltage relay 144 switch to couple the driver circuit 132 and high voltage output 146 to Cockcroft-Walton multiplier 142. This circuitry requires relay control logic 148 to be linked to control circuit 130, low voltage relay 134 and high voltage relay 144, in order to control the switching of relays 134 and 144. The circuitry used in the prior art of FIG. 1C makes significant advancements over the manual techniques illustrated in FIGS. 1A and 1B. However, the relay technique of FIG. 1C requires a high voltage relay (e.g. high voltage relay 144) which requires an expensive vacuum relay. Vacuum relays are expensive, due to the clean room production requirements, and are limited to maximum operating voltages based on the currently available technology. Furthermore, the high voltage relay technique requires two high voltage output circuits, a low voltage relay to switch the converter to the desired output, a high voltage relay to switch the output circuit to the appropriate polarity, and significant control circuitry to ensure no damage occurs to the relay and output circuits during switchover transitions. Accordingly, it is desirable to provide a high voltage power supply capable of being used in today's automated systems, wherein the expense of manufacture is decreased by eliminating the requirement of expensive high voltage vacuum relays, and the expense of providing dual multiplier circuits.